ICM7216D 查看數據表（PDF） - Harris Semiconductor
零件编号
产品描述 (功能)
生产厂家
ICM7216D Datasheet PDF : 17 Pages
| |||
ICM7216A, ICM7216B, ICM7216D
Description
INPUTS A and B
COUNTED
TRANSITIONS
INPUTS A and B are digital inputs with a typical switching
threshold of 2.0V at VDD = 5.0V. For optimum performance
the peak-to-peak input signal should be at least 50% of the
supply voltage and centered about the switching voltage.
When these inputs are being driven from TTL logic, it is
desirable to use a pullup resistor. The circuit counts high to
low transitions at both inputs. (INPUT B is available only on
lCM7216A and lCM7216B).
INPUT A 4.5V
0.5V
50ns MIN
50ns MIN
tR = tF = 10ns
FIGURE 9. WAVEFORM FOR GUARANTEED MINIMUM fA(MAX)
FUNCTION = FREQUENCY, FREQUENCY RATIO,
UNIT COUNTER
Note that the amplitude of the input should not exceed the
device supply (above the VDD and below the VSS) by more
than 0.3V, otherwise the device may be damaged.
Multiplexed Inputs
The FUNCTION, RANGE, CONTROL and EXTERNAL
DECIMAL POINT inputs are time multiplexed to select the
function desired. This is achieved by connecting the appro-
priate Digit driver output to the inputs. The function, range
and control inputs must be stable during the last half of each
digit output, (typically 125µs). The multiplexed inputs are
active high for the common anode lCM7216A and active low
for the common cathode lCM7216B and lCM7216D.
Noise on the multiplex inputs can cause improper operation.
This is particularly true when the unit counter mode of
operation is selected, since changes in voltage on the digit
drivers can be capacitively coupled through the LED diodes
to the multiplex inputs. For maximum noise immunity, a 10kΩ
resistor should be placed in series with the multiplexed
inputs as shown in the application circuits.
Table 1 shows the functions selected by each digit for these
inputs.
TABLE 1. MULTIPLEXED INPUT FUNCTIONS
FUNCTION INPUT (Pin
3, lCM7216A and B
Only)
RANGE INPUT, Pin 14
CONTROL INPUT,
Pin 1
External DP INPUT (Pin
13, ICM7216D Only)
FUNCTION
DIGIT
Frequency
D1
Period
D8
Frequency Ratio
D2
Time Interval
D5
Unit Counter
D4
Oscillator Frequency
D3
0.01s/1 Cycle
D1
0.1s/10 Cycles
D2
1s/100 Cycles
D3
10s/1K Cycles
D4
Display Off
D4 and
Hold
Display Test
D8
1MHz Select
D2
External Oscillator Enable
D1
External Decimal Point
D3
Enable
Decimal point is output for same digit
that is connected to this input.
INPUT A OR 4.5V
INPUT B 0.5V
MEASURED
INTERVAL
250ns
MIN
250ns
MIN
tR = tF = 10s
FIGURE 10. WAVEFORM FOR GUARANTEED MINIMUM fB(MAX)
AND fA(MAX) FOR FUNCTION = PERIOD AND TIME
INTERVAL
Function Input
The six functions that can be selected are: Frequency,
Period, Time Interval, Unit Counter, Frequency Ratio and
Oscillator Frequency. This input is available on the
lCM7216A and lCM7216B only.
The implementation of different functions is done by routing
the different signals to two counters, called “Main Counter”
and “Reference Counter”. A simplified block diagram of the
device for functions realization is shown in Figure 11. Table 2
shows which signals will be routed to each counter in
different cases. The output of the Main Counter is the
information which goes to the display. The Reference
Counter divides its input by 1, 10, 100 and 1000. One of
these outputs will be selected through the range selector
and drive the enable input of the Main Counter. This means
that the Reference Counter, along with its' associated
blocks, directs the Main Counter to begin counting and
determines the length of the counting period. Note that
Figure 11 does not show the complete functional diagram
(See the Functional Block Diagram). After the end of each
counting period, the output of the Main Counter will be
latched and displayed, then the counter will be reset and a
new measurement cycle will begin. Any change in the
FUNCTION INPUT will stop the present measurement
without updating the display and then initiate a new
measurement. This prevents an erroneous first reading after
the FUNCTION INPUT is changed. In all cases, the 1-0
transitions are counted or timed.
13-29
Share Link: 